Olefins, also commonly known as alkenes, are important items of commerce. Their many applications include employment as intermediates in the manufacture of detergents, as more environmentally friendly replacements where refined oils might otherwise be used, as monomers, and as intermediates for many other types of products. An important subset of olefins are olefin oligomers, and one method of making olefin oligomers is via oligomerization of ethylene, which is a catalytic reaction involving various types of catalysts. Examples of catalysts used commercially in polymerization and oligomerization of olefins include alkylaluminum compounds, certain nickel-phosphine complexes, and a titanium halide with a Lewis acid, such as diethyl aluminum chloride.
Another group of olefin polymerization catalysts is derived from pyridine bis-imines. With catalysts of this type, a nitrogen-based ligand engages in a coordination reaction with a transition metal salt. The coordination reaction forms a metal complex, which is a catalyst precursor. The metal complex further reacts with another precursor or activator to generate a metal alkyl or metal hydride species. The catalyst resulting from the generation of the metal alkyl or metal hydride species polymerizes olefins.
Applications and demand for olefin polymers and oligomers continue to multiply, and competition to supply them correspondingly intensifies. Thus, additional novel and improved catalysts and methods for olefin polymerization and oligomerization are desirable.